1. Field of the Invention
The present invention relates to a silicone antifoaming composition free from inorganic filler material, and which comprises a diorganopolysiloxane (A), and MQ resin (B) and a cyclic polydiorganosiloxane (C).
2. Description of the Prior Art
It is known to this art that certain silicones, if desired in combination with siliceous inorganic fillers, exhibit antifoaming properties and can be employed by virtue of this property in foaming systems which are aqueous (for example in detergents) and/or nonaqueous (for example petroleum products).
Thus, U.S. Pat. No. 4,145,308 describes that an aqueous emulsion of the combination (A) and (B) by itself, or preferably together with silica and, if desired, with oleic acid, has an antifoaming effect.
U.S. Pat. No. 3,455,839 describes the use of an antifoam composition for an aqueous system comprising the constituents (A) and (B) together with a siliceous inorganic filler, and U.S. Pat. No. 4,486,336 suggests the use of two silicone oils of different viscosities for (A) as an improvement over the compositions of the '839 patent.
U.S. Pat. No. 4,082,690 describes an antifoam composition for a nonaqueous system, which is a combination of the constituents (A) and (B) together with a hydrocarbon solvent.
U.S. Pat. No. 4,104,186 describes, as an antifoam composition, the combination of (A) with a methylsilses-quioxane resin consisting essentially of a T unit, adapted more particularly for detergent compositions. This antifoam is preferably combined with treated silica.
An antifoam composition comprising only the constituents (A) and (B) (U.S. Pat. No. 4,145,308) has a very good antifoaming capacity, but this binary combination, not dissolved in a hydrocarbon solvent, has no practical use because of its very high viscosity.
If a treated silica is added (U.S. Pat. No. 3,455,839) to this binary combination of (A) and (B), a more fluid antifoam is indeed obtained, but there is a risk that the silica may settle out during storage. Moreover, an antifoam of this type cannot be employed for petroleum media because of the presence of silica and, as a general rule, in systems to be treated where a solid filler is undesirable.
If a hydrocarbon solvent is added instead of silica (U.S. Pat. No. 4,082,690) to this binary combination of (A) and (B), an antifoam is obtained which is suitable for nonaqueous media, but which is unsuitable for aqueous media, in particular for use with detergents.